[Help-bash] Unexpected return from subscripts

[Zhong Wang]

Hi all,

We met a very weird problem with bash "version 
3.00.15(1)-release" running on a RedHat server. We are using a hadoop-test script to test whether a
 file exists on HDFS. But we observed several times that the hadoop-test
 script, which is a subscript in a control-flow script, returned 
unexpectly. It seems the subscript was put in *background*, and the 
main-control script just go on and got a wrong return value. We added 
some debug log in the hadoop-test script, and it looks like this:

============== sh -x DEBUG LOG ==============
+ /home/work/hadoop-client/

hadoop/bin/hadoop dfs -test -e xxxFile
+ '[' 0 -ne 0 ']'    # this is unexpected, the real return value is 1.
+ some other things...
+ ...
+ ...
+ test: File does not exists: xxxFile    # this is unexpeted, should be printed before the condition statement. Looks like test script goes to *background*
+ ...
=============================================

The scripts are simple enough and we could make sure this is not a programming problem. It looks like subscripts are put to *background* unexpectly. We are not sure this is whether a kernel bug or bash bug.

This problem bothered us for several months because we have a large cluster with thousands of nodes running the hadoop-test script. We met this case every month. Anybody ever met the same problem?

Thanks,
Zhong